Page d'accueil // FSTC // Actualités // Atomistic Modelling Seminar: Taming electrons in 2D materials: influence of substrates, defects and Moiré superlattices.

Atomistic Modelling Seminar: Taming electrons in 2D materials: influence of substrates, defects and Moiré superlattices.

twitter linkedin facebook google+ email this page
Add to calendar
Conférencier : Mit H Naik
Date de l'événement : lundi 16 juillet 2018 11:00 - 12:30
Lieu : Campus Limpertsberg - Batiment des Sciences BSC 2.04

Effect of the dielectric environment and defects on the electronic structure are important considerations in the design of devices using 2D materials.
Using ab initio density functional theory (DFT) and GW calculations, we study the effect of substrate screening on the quasiparticle band gap and defect charge transition levels in monolayer MoS$_2$. We find a giant renormalisation to the free-standing quasiparticle band gap by 350 meV and 530 meV in the presence of graphene and graphite as substrates, respectively. Our calculation on sulphur vacancy defects using the  DFT+GW formalism reveals two charge transition levels, (+1/0) and (0/-1), in the pristine band gap of MoS$_2$. In the presence of substrates, these CTLs continue to lie in the band gap and are pinned to the band edges.
 
Ultraflat bands in twisted bilayers of two-dimensional materials have a strong potential to host strongly-correlated phases. Using DFT calculations, we show the emergence of ultraflat bands at the valence band edge in twisted bilayer MoS2. The computed band widths, 5 meV and 15 meV for 56.5 and 3.5 degree twist angles, respectively, are comparable to that of twisted bilayer graphene near ’magic’ angles. Large structural transformations in the Moiré
patterns lead to formation of shear solitons at stacking boundaries and strongly influence the electronic structure.
 
References:
Ultraflat bands and shear solitons in Moiré patterns of twisted bilayer transition metal dichalcogenides
Substrate screening effects on the quasiparticle band gap and defect charge transition levels in MoS2